Motor fuels



Patented Oct. 8 1946 MOTOR FUELS Anthony E. Robertson, Roselle, N. J.,assignor to Standard Oil Development Company, a corporation of DelawareNo Drawing. Application January 1, 1944, Serial No. 516,711

9 Claims. (01314-53) In this invention selected alcohols properlyblended with certain low molecular weight hydrocarbons provide valuablequick-starting fuels for high-compression spark-ignition engines. Thesefuels are of special value for developing maximum power and thermalefiioiency in high output engines with freedom from vapor lockingdifiiculties.

Although it has been known that alcohols, such as methyl or ethylalcohol, either pure or blended with gasoline have some advantages asmotor fuels, mainly that of high octane rating, they have only limiteduse in countries where adequate petroleum supplies are readilyavailable. The alcohol-gasoline blends introduce certain operatingdiliiculties; for example, a small amount of water causes separation ofthe alcohols from the gasoline, meaning that these blends have low watertolerance. These blends, moreover, are subject to vapor lockingdifficulties, which are more serious than such difliculties incident tothe use of the gasoline without the addition of alcohol. The use of thepure alcohols would be advantageous for power, anti-detonating quality,and water tolerance, but the pure alcohols have poor startingcharacteristics.

In accordance with the present invention, disadvantages ofalcohol-gasoline blends and pure alcohols as motor fuels are overcome byblending from to by volume of a selected low molecular weighthydrocarbon component having from 3 to 5 carbon atoms per molecule, witha major proportion of an alcohol having from 1 to 5 carbon atoms permolecule.

I have found that blends of these selected compounds in the properproportions are not subject to phase separation, even if a considerableamount of water is added. Ihave also found that these blendssatisfactorily keep in storage without excessive vapor loss andsatisfactorily mix with intake air on being carbureted for obtainingquick starting of a cold motor. These blends exhibit extraordinaryfreedom from vapor lock in carbureting systems designed and set for usewith ordinary hydrocarbon fuels. In comparison to all alcohol containingfuels hitherto proposed, the exceptional properties of the blends hereinprovided are of tremendous advantage,

In order to obtain a desired efficiency with these fuel blends, it isimportant that the volatile hydrocarbon component be blended in aproportion of at least 5% of the blended components and should be lowerboiling, or of greater volatility, than hexanes or hexenes. Methane,ethane, and ethylene are at the other extreme, in being too low boiling.Limitations on selection 2 and proportioning of the hydrocarboncomponent are dependent on proper air to fuel ratios in average fuelinduction systems.

Fuel blends of the present invention have certain peculiarcharacteristics in that the low boiling hydrocarbon and the alcoholblended in ascertained proportions do not form ideal solutions butexhibit abnormally large deviations from Raoults law governing idealsolutions. These deviations appear significant for satisfactory airfuelratios with blends herein described. Small amounts of lower and higherboiling hydrocarbons, such as, ethane or hexane, incidentally present inthe composition do not destroy the value of the fuel for the intendedpurpose,

The upper limit of the hydrocarbon component proportion restricted inaccordance with empirical determinations on Vapor lock tendencies of theblends; for example, a blend of more than 10% of isopentane in ethanol,or more than 10% butane in isopropanol or butanol, at ordinaryatmospheric temperatures causes vapor lock in the average fuel system.Thus, about 10% by volume of the hydrocarbon component is the upperpractical limit.

Blends of between 5% and 10% by volume of the volatile hydrocarboncomponent with to 90% by volume of the alcohol component exhibitdesirable properties of quick-starting, high antiknock quality, lowvapor-locking tendency and high-power output.

Alcohols used as a major ingredient of the blends are preferablymonohydric aliphatic alcohols (alkanols) of 1 to 5 carbon atoms permolecule, Ethyl and methyl alcohols, on account of their availabilityand large deviations from ideal solutions in the desired blends areuseful.

Of alcohols higher boiling than ethyl alcohol, isopropyl and secondarybutyl alcohols are outstanding for present purposes. Other alcoholshigher boiling than ethyl, but with less preference, are n-propyl,n-butyl, tertiary-butyl, isobutyl, ter-amyl, n-amyl, and sec-amylalcohols. The preferred alcohols have normal boiling points below C. Itis desirable to omit alcohols boiling above C.

Blends formulated for the practice of this invention have unusualdistillation and vapor pressure characteristics, which enable them toform a vapor charge which undergoes quick ignition in cold motors atsub-zero temperatures. These blends remain homogeneous even with 10 ormore volumes of water added per 100 volumes of the blend. They remainsatisfactorily constant in composition and purity for suitable periodsof.

3 time for use under various operating conditions.

For illustration, characteristics of blends forming specific embodimentsof this invention are presented in the following table:

4 throughout the boiling range of the fuel being increased. Thisbalancing of the volatility is desirable for more uniform distributionof the combustible mixture. Thus, in characteristics Table I InitialWater toler- 907 d1s- Dist. Reid vapor boiling ance vols. of BlendComposition tilled ofl loss pressure point water/100 F. at a percentvols. oi blend 5% n-pentane in methanol 7.9 122 149 1. 22. 4 10%n-pentane in methanol 11. 4' 88 149 0.8 11.9 isopentane in ethanol 5.7.185 .178 l. 7 38. 5 10% isopentane in ethanol... 9. 4 97 178 1. 5 29. 55% butane cut in isopropanol 8.3 131 179 1.9 111. 0 5% butane cut inbutanol 7. 6 185 241 5.0 16. 7

The butane cut used in blends 5 and 6 is otherwise known as plantbutane, which contains approximately 60 to 70% n-butane, to lsobutane,and 10 to 20% butenes:

Another remarkable characteristic of the new 20 of prime importance forengine performance, the

and volatility distribution of the blends. To illustrate this phase ofthe invention, the following examples are given:

EXAMPLES Blends of n-pentane and isopropyl alcohol were made up withvarying amounts of water then subjected to tests for determination oftheir volatility and vapor pressure characteristics. The compositions ofthe blends and the inspections obtained on them are summarized below:

Table II Blend No.

Vol. per cent n-pentane 10 10 10 10 Vol. per cent isopropanoL 90 80 7000 Vol. per cent of water 0 10 20 Inspections:

Gravity, A. P. I 50. 5 43.6 38.2 33.0 Reid V. P., #/sq. in 5. 0 6. 7 11.l 13. 5 A. S. T. M. dist.-

I. B. P., F 122 97 95 91 Per cent at 158 11. 8.0 9. 5 11.0 12. 5- Percent at 212 F 94.0 84 90% at 180 176 100 212 Dist loss, per cen 2.0 1.01.0 1.0

By investigation of engine performance with ited amounts of about 10,20, and 30%, the Reid vapor pressure is increased, while at the sametime, the blend is given substantial improvement in volatility balance,the amounts of the fuel vaporized at different intermediate temperaturesplaces minor proportions of alcohol, in the lim-',

aqueous alcoholic solutions containing correct amounts of the highlyvolatile hydrocarbons are fully satisfactory.

As previously set forth, regardless of whether the fuel blend containswater or is substantially free from water, it should preferably containa hydrocarbon component blended in a proportion of about 5 to about 10%by volume in order to give the blend the desired advantageouscharacteristics noted. The alcohol component constituted of one or morealkanols having 1 to 5 carbon atoms per molecule is the major ingredientof the fuel blend, 1. e., the alcohol, whether anhydrous or aqueous iblended in an amount oi at least 60%.

When water is present in the fuel blend to form what is termed anaqueous alcohol component, the proportion of water added should notexceed that amount which is above the water tolerance of the blend,moreover, preferably it should not exceed about 30% by volume.

The ordinarily most useful fuel blends of the present invention areformulated from to 1 part by volume of the 3 to 5 carbon atomhydrocarbon component blended with 6 to 9 parts by volume of the 1 to 5carbon atom alcohol component and with from 0 to 3 parts by volume ofwater, the combined parts by volume of the alcohol component and of thewater being blended with; the hydrocarbon component in a volume ratio ofat least about 9 to 1, so that the aqueous alcohol forms at least aboutby volume of the fuel.

It is not intended to limit the invention to the specific blends shownin th foregoing tables. It will be observed that these tables illustratehow the blends are obtained with varying characteristicsjso that for aspecific purpose, the most efiicient blend is provided.

If requirements of a carbureted engine are such that the Reid vaporpressure must come within the range of'l to 7.5 or 8 pounds per squareinch, as in the case of aviation motors, blends meeting this requirementare available among th foregoing types of blends. For example, a blendbetween 5% and 10% of isopentane in ethanol will clearly have a Reidvapor pressure meeting these requirements. Other properly chosencombinations of the hydrocarbons and alcohols also meet thisrequirement.

It is to be noted that the preferred blends are obtained by selecting arelatively higher molecular weight hydrocarbon for blending with a lowermolecular weight alcohol, e. g., a C4 to C5 hydrocarbon with a C1 to C2alcohol, vice versa, a lower hydrocarbon blended with a higher alcohol,e. 3.,

5. a C3 or C4 hydrocarbon with a C3 to C5 alcohol, or with modificationby added water. However, for an average automotive engine, blendssatisfactorily used have Reid vapor pressures ranging from 5 to as highas about 13 pounds per square inch at 100 F., or even slightly higher incold climates.

One way of eficiently and economically using the disclosed blends is tosupply the carburetor of the engine from an individual tank separatefrom the main supply tank, so that the alcohol blend can be fed to theengine for starting at low temperatures or acceleration at high power.

The advantageous blends described may also contain small amounts ofother ingredients ordinarily useful in motor fuels, e. g., a fraction of1%of an anti-knock agent, such as tetraethyl or tetramethyl lead. Theymay also contain a small amount of a dye, thickening agent, orlubricant. By a small amount is meant generally less than about 1%.

The volatile hydrocarbon component, as indicated, is preferably a 3 to 5carbon atom paraffinic hydrocarbon which is resistant to oxidation andreadily available in highly purified form; hence, in general, thedisclosed blends are easily obtained in a chemically stable form.

The hydrocarbon component may also contain or be composed of unsaturatedhydrocarbons having 3 to 5 carbon atoms per molecule. Such unsaturatedhydrocarbons may be mono-olefins or diolefins, but preferably theunsaturated hydrocarbons should not contain more than one double bond,i. e., should not be more unsaturated than a mono-olefin. Also, the 3 to5 carbon atom cycloalkanes or cycloalkenes may be used. Thus, ingeneral, suitable hydrocarbons for the hydrocarbon component may becharacterized as 3 to 5 carbon atom molecules containing no more thantwo double bonds and preferably no more than one double bond.

The alcohol component may contain small amounts of other low boilingoxygen-containing compounds, such as ethers, ketones, aldehydes, andesters, but ordinarily these should not be present in any substantialamounts to avoid upsetting the effective balance between the preferredcomponents in the blend.

The present application is a continuation-inpart of application SerialNo. 370,787 filed-December 19, 1940, now Patent No. 2,365,009, datedDecember 11, 1944, the claims of which read on a motor fuel containing asubstantial amount of water as an essential constituent. The purpose ofthe present application is to claim motor fuels not containing water butwhich do contain a major proportion of a branched alcohol and a minoramount of a light hydrocarbon of about 3 to 5 carbon atoms.

Some experimental data have already been given above as to blend ofisopropyl alcohol containing in one case 5% of butane and in anothercase of normal pentane. Other satisfactory blends which are preferredeven over the above two examples, are blends of isopropyl a1- cohol witheither isobutane or isopentane or a light cycloalkane such ascyclopentane, because these blends exhibit superior performance whenlead tetraethyl is added to them for use in especially high octanenumber aviation engines.

The term branched alcohol of 3 to 5 carbon atoms is intended to includeisopropyl alcohol which is branched in View of the linkage of thehydroxyl group to the middle of the 3 carbon atoms, as well as secondaryor tertiary butyl and amyl alcohol, and even the primary amyl alcoholswhich contain a branched hydrocarbon structure, such as tertiary butylcarbanol and 2- methyl or 3-methyl'butano1.

When such fuels are prepared without the addition of any water, thebranched alcohol should constitute about 80-95% by volume of the fueling 80-95% of isopropyl alcohol and 20-5% of a branched paraflinichydrocarbon of 4-5 carbon atoms, such as isopentane, or a cyclo parafflnsuch as cyclopentane.

There are obviously a number of modifications which come within thespirit of this invention and it is not intended that the invention asdefined in the appended claims be limited to the specific examples thathave been given for the purpose of illustration.

I claim:

1. A motor fuel comprising about 80 to 95% of a branched alkanol of 3 to5 carbon atoms and a minor proportion suificient to raise the Reid vaporpressure of the blend to at least 5 lbs. per square inch at 100 F. butnot more than about 1 3 lbs. per square inch at 100 F. of a normallygaseous hydrocarbon of 3 to 5 carbon atoms selected from the groupconsisting of aliphatic and cyclo-aliphatic hydrocarbons.

2. A motor fuel having a Reid vapor pressure of about 5 to 13 lbs. persquare inch at 100 F. containing about 5% to 10% of 3 to 5 carbon atomshydrocarbons containing no more than 2 double bonds per moleculeselected from the group consisting of aliphatic and cyclo-aliphatichydrocarbons, and a major proportion of a 3 to 5 carbon atoms branchedalkanol.

3. A motor fuel having a Reid vapor pressure of about 5 to 13 lbs. persquare inch at 100 F.

I comprising about 80 to 95% by volume of'isoproyl alcohol and about20-5% of a hydrocarbon of 4 to 5 carbon atoms selected from the groupconsisting of aliphatic and cyclo-aliphatic hydrocarbons.

4. A motor fuel having a Reid vapor pressure of about 5 to 13 lbs. persquare inch at 100 F. particularly adapted for quick cold starting andhigh power output, comprising about to 95% of isopropyl alcohol andabout 20-5% of a branched 4 to 5 carbon atoms parafiinic hydrocarbon.

5. A motor fuel according to claim 4 in which the light hydrocarbon is apentane. I

6. A motor fuel according to claim 4 comprising about of isopropylalcohol and about 10% of isopentane.

7. A motor fuel having a Reid vapor pressure of about 5 to 13 lbs. persquare inch at 100 F. comprising about 80 to by volume of a branchedalkanol of 3 to 5 carbon atoms, and about 20-5% of a mixed C4 aliphatichydrocarbon fraction.

8. Motor fuel according to claim 1 containing a small amount of a leadalkyl anti-knock agent.

9. Motor fuel according to claim 3 containing small amounts oftetraethyl lead.

ANTHONY E. ROBERTSON.

